<template>
    <div class="pagination">
        <!-- top -->
        <button :disabled="pageNo === 1" @click="pageNoHandle(pageNo - 1)">上一页</button>
        <button v-if="startAndEndNumber.startNum > 1" @click="pageNoHandle(1)" :class="{active: pageNo === 1}">1</button>
        <button v-if="startAndEndNumber.startNum > 2">...</button>
        <!-- middle -->
        <button v-for="(page, index) in startAndEndNumber.endNum" :key="index" v-if="page >= startAndEndNumber.startNum"
                @click="pageNoHandle(page)" :class="{active: pageNo === page}">{{page}}</button>
        <button v-if="startAndEndNumber.endNum < totalPage - 1">...</button>
        <button v-if="startAndEndNumber.endNum < totalPage" @click="pageNoHandle(totalPage)" :class="{active: pageNo === totalPage}">{{totalPage}}</button>
        <!-- bottom -->
        <button :disabled="pageNo === totalPage" @click="pageNoHandle(pageNo + 1)">下一页</button>
        <button style="margin-left: 5px;">当前：{{pageNo}}</button>
        <button style="margin-left: 30px;">共{{total}}条</button>
    </div>
</template>

<script>
    export default {
        name: "Pagination",
        props: ["pageNo", "pageSize", "total", "continues"],
        methods: {
            pageNoHandle(page) {
                this.$bus.$emit("get_page_number", {page});
            }
        },
        computed: {
            totalPage() {
                return Math.ceil(this.total / this.pageSize); // 向上取整
            },
            startAndEndNumber() {
                // 当前页码起始数字，continues(连续的页数) 规定 >= 5
                let startNum = 0, endNum = 0;
                if (this.continues > this.totalPage) {
                    startNum = 1;
                    endNum = this.totalPage;
                } else {
                    startNum = this.pageNo - parseInt((this.continues / 2));
                    endNum = this.pageNo + parseInt((this.continues / 2));
                    if (startNum < 1) {
                        startNum = 1;
                        endNum = this.continues;
                    }
                    if (endNum >= this.totalPage) {
                        startNum = this.totalPage - this.continues + 1;
                        endNum = this.totalPage;
                    }
                }
                return {startNum, endNum};
            }
        }
    };
</script>

<style lang="less" scoped>
    .pagination {
        text-align: center;

        button {
            margin: 0 5px;
            background-color: #f4f4f5;
            color: #606266;
            outline: none;
            border-radius: 2px;
            padding: 0 4px;
            vertical-align: top;
            display: inline-block;
            font-size: 13px;
            min-width: 35.5px;
            height: 28px;
            line-height: 28px;
            cursor: pointer;
            box-sizing: border-box;
            text-align: center;
            border: 0;

            &[disabled] {
                color: #c0c4cc;
                cursor: not-allowed;
            }

            &.active {
                cursor: not-allowed;
                background-color: #409eff;
                color: #fff;
            }
        }
    }

    .active {
        background: skyblue;
    }
</style>
